The present invention refers to a fire detector, and in particular to a fire detector of the type having a scattered light detector unit and an ionization detector unit which are operatively connected to a common system evaluator.
The brochure C 3001 6/84 of the company BRK Electronics describes a fire detector of this type by which an early detection of fire is made possible without increasing the frequency of faulty alarms. The principle of this fire detector is based on the fact that the ionization detector unit responds to the presence of small aerosol particles while the scattered light detector unit reacts early to the presence of large aerosol particles because of their high scattering capability. This conventional fire detector includes a housing which accommodates the ionization detector unit and the scattered light detector unit in separate compartments, with both detector units communicating with separate air inlet openings. Therefore, this fire detector is of comparably large diameter, with only one of the detector units including circumferentially spaced air inlet openings and thus having a responsiveness which is essentially independent of the direction of flow.